Looking at the 07 SM drawings, guessing the blower motor unit fire wall seal where the intake air comes in from outside. Ram air seems to effect it the way you describe the condition. This is a guess--If you can get the grill removed where the O/S air comes in under the wipers you may be able to use a mirror to check it and if bad, seal it with RTV silicone sealer. Getting at the A/C unit under the dash looks to be major job.